容器安装后'subscript(_:)'的模棱两可的使用

Question

将 Firebase/Firestore 添加到我的 pod 文件并运行 pod 安装我的应用后，报告 4 在下面的代码中模棱两可地使用"下标(_：("消息：让 monToFri，让坐，让纬度和让经度。如何纠正这种情况？

func displayAnnotations() {

if Reachability.isConnectedToNetwork() {

let ref = Database.database().reference()
ref.child("Postbox").observe(.childAdded, with: { (snapshot) in

let monToFri = (snapshot.value as AnyObject?)!["Monday to Friday Collection Time"] as! String?
let sat = (snapshot.value as AnyObject?)!["Saturday Collection Time"] as! String?
let latitude = (snapshot.value as AnyObject?)!["Latitude"] as! String?
let longitude = (snapshot.value as AnyObject?)!["Longitude"] as! String?

let lastCollection = "Mon - Fri: (monToFri!)" + " Sat:  (sat!)"

let annotation = MKPointAnnotation()
annotation.coordinate = CLLocationCoordinate2D(latitude: (Double(latitude!))!, longitude: (Double(longitude!))!)
annotation.title = "Last Collection:"
annotation.subtitle = lastCollection

self.mapView.addAnnotation(annotation)

self.allAnnotations.append(annotation)
self.allIds.append(snapshot.key)
self.postboxesLoggedLabel.text = String(self.mapView.annotations.count)

})
} else {

print("Internet Connection not Available!")

let alertController = UIAlertController(title: "No Internet Connection", message: "Make sure your device is connected to the internet.", preferredStyle: .alert)

// Create the actions
let okAction = UIAlertAction(title: "OK", style: UIAlertAction.Style.default) {
UIAlertAction in
NSLog("OK Pressed")
}

// Add the actions
alertController.addAction(okAction)

// Present the controller
self.present(alertController, animated: true, completion: nil)
}

}

Answer 1

为什么每次使用时都下标 snapshot.value？

let ref = Database.database().reference()
ref.child("Postbox").observe(.childAdded, with: { (snapshot) in
let data = snapshot.value as? NSDictionary
let monToFri = data!["Monday to Friday Collection Time"] as? String ?? "Empty String" 
// Other code....
}